Back in Sweden, Nobel devoted himself to the study of explosives. He was particularly interested in the safe manufacture and use of nitro-glycerine, a highly unstable explosive. Nobel's brother Emil had been killed in a nitro-glycerine explosion in 1864. Nobel incorporated nitro-glycerine into silica, an inert substance, which made it safer and easier to manipulate. This he patented in 1867 under the name of 'dynamite'.